This application claims the priority benefit of Taiwan application serial no. 90116427, filed Jul. 5, 2001.
1. Field of the Invention
The invention relates in general to a method of fabricating an organic light emitting diode (OLED), and more particularly, to a method of using sprayed fluid to dissolve the organic material or water soluble material, and using a venting system such as a vacuum system to absorb the dissolved organic or water soluble material to pattern the organic material or the water soluble material.
2. Description of the Related Art
The organic light emitting diode includes an organic thin film with luminescence property sandwiched between two electrodes. While applying a voltage between 2 Volts to 10 Volts, holes are injected from anode and electrons are injected from cathode to the luminescent organic thin film. The potential generated by the external electric field causes the carriers to move and recombine within the thin film. A part of energy released by the recombination of the electron and hole pairs excites the luminescent molecules to single-excited-state molecules. When the single-excited-state molecules fall back to the ground state, a certain proportion of the energy is released in a form of photons to generate luminescence. This is the luminescence mechanism for the organic light emitting diode. Typically, the model of mobile charges is the energy band model. However, different from metal or semiconductor material having certain band width, the energy band of organic material is referred as the continuous energy band formed by electrons and holes. Applying such a model, the process of the photons being released by recombination in the energy band gap after injecting charges from electrodes is easily introduced.
FIG. 1 shows a flow chart of a method for fabricating a conventional organic light emitting diode. A transparent substrate is provided. Multiple strip like anodes are formed on the transparent substrate in step S100. The material of the anodes includes indium tin oxide (ITO). A global coating process is performed to form a multi-layer structure made up of an organic luminescence layer, hole transport layer, hole injection layer, electron transport layer and electron injection layer in step S102. Since the multi-layer structure of the organic light emitting diode has the property of easily absorbing moisture, a pattern process is required before encapsulating the multi-layer structure (S104). The pattern process includes removing a part of the multi-layer structure between the light emitting diodes, so as to define the light emitting diodes on the substrate. The multi-layer structure with the hydrophilic property is then wrapped with the encapsulation material. The penetration of water and oxygen molecules that affect the electric performance of the device is thus prevented.
Further referring to FIG. 1, a plurality of strip like cathodes are formed on the luminescent layer in step S106. The organic light emitting diode array is thus formed. After completion of the organic light emitting diode array, an encapsulation process is performed in step S108, followed by a die cutting step as denoted as S110 to cut the substrate into a plurality of organic light emitting diodes.
In step S104, the conventional method of removing the multi-layer structure includes using a tool such as cotton to wipe the edge of the transparent substrate, or using a laser to wipe the edge, so as to remove the unwanted multi-layer structure on the edge of the organic light emitting diodes. Alternatively, a mask process is performed on the substrate to form the patterned organic luminescent layer and hole transport layer.
Drawbacks exist for the manual or laser edge wiping and the mask process. The manual edge wiping consumes great labor and cost, so that a mass production cannot be achieved. The laser edge wiping and the mask process have the problem of high fabrication cost.
The invention uses a nozzle to spray a fluid that dissolves the organic or water-soluble material to be removed from the multi-layer structure made up of the organic luminescent layer, hole transport layer, hole injection layer, electron transport layer, and electron injection layer. The dissolved material is then vented or vacuumed away. The patterning of the multi-layer structure can thus be obtained. After patterning, an encapsulation step is performed to wrap the multi-layer structure made up of an organic luminescent layer, hole transport layer, hole injection layer, electron transport layer, and electron injection layer to isolate the oxygen and water molecules. The probability for the cathode to react with oxygen and water molecules is reduced, and the lifetime of the device is effectively increased.
The material to be removed with the fluid sprayed from the nozzle is not limited to organic luminescent layer, hole transport layer, hole injection layer, electron transport layer, and electron injection layer. The fluid sprayed from the nozzle can also be applied to remove other organic or water-soluble material.
Both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.